The present invention relates generally to satellite communication systems, and more particularly, to a communication protocol for use with a high data rate satellite communication system that provides data, voice and video communication between individuals.
The past several decades has seen the development of communications systems that have provided for the real-time distribution of information on a global scale. The development of these global communication systems has evolved along several paths that use either ground-based or satellite-based communication. Satellite-based systems have been employed for many years to distribute voice, data and video signals for global broadcasting of news and sporting events, for example. With the advent of newer high power satellite systems and technology, direct broadcast television systems are available that provide for broadcasting of television signals from up to 100 stations using a single satellite. Individuals install an antenna and a satellite receiver that receives the broadcasts directly by way of the satellite and display them on a television monitor.
In order to provide for more personal communication or teleconferencing between individuals, companies such as AT&T, for example, have developed a video telephone system that employs a small (3-4 inch) television monitor in combination with a conventional telephone. The video telephone system typically uses fiber optic links to provide a sufficient bandwidth to carry the video along with the voice signals. However, this type of system does not have enough bandwidth to provide for full motion video.
For many years multitudinous standards and protocols have been available for placing calls, setting up connections, monitoring communication link status, and tearing down calls on the terrestrial phone network, and also for establishing communications over data networks, and more recently, for transmission of digitized voice and data over a common network (ISDN). Furthermore, very small aperture terminal (VS AT) networks, consisting of a satellite, a hub, and many small VSAT user terminals have had the ability to transmit digital voice and data, interfacing almost transparently with terrestrial satellite networks. In this type of network link the satellite acts as a bit pipe, providing a network link between two terrestrial nodes, and is a two-hopped system with a hub in the middle to route calls, or packets.
In order to provide for an even more cost-effective solution to personal telecommunication needs, the assignee of the present has developed a high data rate satellite communication system that provides for the communication and distribution of full motion video, voice and data signals, to provide for personal teleconferencing between individuals. This system is disclosed in U.S. patent application Ser. No. 08/142,524, filed Oct. 21, 1993, entitled "High Data Rate Satellite Communication System", the contents of which are incorporated herein by reference. This high data rate satellite communication system comprises a plurality of very small user terminals (VSAT's) that ,are linked by and that communicate with each other by way of a satellite relay system. A network control center provides control signals that control the satellite relay system and coordinate linking of terminals to each other. The system employs frequency division multiplexing on uplinks from the terminals and the network control center to the satellite relay system. The system employs time division multiplexing on downlinks from the satellite relay system to the terminals and the network control center. However, other uplink and downlink multiplexing schemes may also be used.
However, in this new system, the satellite does not act like a link in the network. Interactive services, such as personal videoconferencing, and the like, will not tolerate a two-hop delay. Because of the on-board switching and routing capability, the satellite acts as a node. This new system must also accommodate a larger number of users, and larger number of potential users for packet switched or circuit switched data, but none-the-less must provide connection-oriented communications, although some connectionless communication may also be provided for. Thus, in this new system, resources are assigned to various communication source and destination terminals on a temporary call-by-call basis.
The satellite in this new system is no longer just a bit-pipe-in-the-sky. In addition to the normal setup protocols used in ISDN, for example, the additional problem of allocating satellite resources such as assigning uplink and downlink physical channels to source and destination user terminals must be solved. This problem is new to multibeam satellite communication architectures using digital traffic, on-board demodulation, routing and remodulation, with or without the use of FDM uplinks and TDM downlinks.
Therefore, because signal routing and switching is performed on-board the satellite of this new system, because this system is a one-hop system, and because the satellite interfaces with the network controller on the ground only when calls are set up, tom down or monitored, a new communication protocol is required to permit transfer of data and control signals between the various components that are interconnected by the system.
Accordingly, it is an objective of the present invention to provide for a communication protocol for use with a high data rate satellite communication system that provides for the communication of data, voice and video between individuals. These protocols build on existing standardized protocols, namely, ISDN. It is a further objective of the present invention to provide for a communication protocol for use with a high data rate satellite communication system that employs frequency reuse and onboard demodulation and routing or switching and a network control center for call setup, monitoring and teardown.